This request is for funds to purchase a four laser BD LSRFortessa multiparameter flow cytometer. This instrument will be housed within the Department of Immunology Flow Cytometry Facility at the University of Pittsburgh School of Medicine. The goal of the core facility is to provide sensitive cell phenotyping and cell sorting capabilities to research groups within the University of Pittsburgh biomedical community. Multicolor flow cytometry is an essential tool that allows immunologists to dissect the development and coordinated interactions of the white blood cells that mediate pathogen defense and anti-tumor activity. The current facility contains an eight year old BD LSR II analytic instrument and a seven year old Aria cell sorter. Our sole analytic instrument is at saturated capacity for supervised applications. The main reason for this proposal is to provide critically needed instrumentation time, under expert supervision, for complex multi-color experiments. Since the Immunology Flow Cytometry Facility commenced operation eight years ago, it has become an integral part of the medical community with more than 40 PHS funded groups within the biomedical research area as well as PHS supported projects with investigators in other departments and at neighboring institutions. The sole multiparameter analytic flow cytometer we house is insufficient to accommodate the number of researchers. We have an immediate demand for a second analytic instrument that parallels our current four laser capabilities. We also have a growing need for a specialty laser, the yellow-green laser, for advanced applications. Therefore, this application requests a four laser BD LSRFortessa flow cytometer (blue, red, violet, UV) which will be supplemented by matching funds from the Department of Immunology for the purchase of a fifth laser (yellow-green). The proposed four laser LSRFortessa allows us to provide users with an instrument that 1) eases the scheduling overload of our analyzer, 2) enables facility personnel to help multiple users simultaneous thereby maximizing research productivity, and 3) with the addition of the yellow-green laser, will culminate in a five laser configuration that is not currently available at the University, and for which there is palpable demand. The PHS funded user base within the institution continues to expand, and Pitt is currently ranked 7th in NIH funding. The cytometer will be purchased from BD Biosciences, a company that ranks 10th among Fortune 500 companies that participate in the US Environmental Protection Agency's Green Power Partnership.